Perisesarma bidens

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Perisesarma bidens

Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Malacostraca
Order:	Decapoda
Infraorder:	Brachyura
Family:	Grapsidae
Genus:	Perisesarma
Species:	P. bidens

Binomial name

Perisesarma bidens
(De Haan, 1835)

Perisesarma bidens, the red-clawed crab or red claw crab, is a species of crab found in the estuaries of Thailand, Japan, Hong Kong, South Korea and Singapore.

Red-clawed crabs are semi-terrestrial, spending most of their time completely submerged in brackish water. They reach maturity in 8 months and their brief lifespan ranges from 2 to 4 years. Their body diameter ranges from 2 to 4 cm with coloration anywhere from dark red to reddish brown, except for the claws which are a consistent bright red, hence their popular name. Sexing is easily done by observing their symmetrical claws. The males have bigger claws as opposed to females which have smaller, overall slimmer claws.

Red-clawed crabs are omnivorous scavengers, feeding on mostly anything they will get their claws (chelipeds) on. A mixed diet of plants and animal matter results in fast growth and great overall health.

[edit] Red-clawed crabs in the aquarium

This species is becoming increasingly popular amongst aquarium hobbyists due to their scavenging nature, but have some minimum requirements that have to be met to ensure their well being. They are best kept in low-end brackish water with a specific gravity ranging from 1.004 to 1.008 ppt, temperature varying from 21 to 29 degrees Celsius (70 to 85 degrees Fahrenheit) and a pH of 7.2 to 8.5. The best choice of substrate is sand to mimic their natural environment, which also allows them to sift through it searching for food. A very important aspect to their well-being in a tank is providing them with access above the water, where they can occasionally dry off and breathe. Being kept in full freshwater with no land access is not feasible for their long-term well being. Although pet stores keep them in the exact opposite conditions (full freshwater with no access to land), that is only a temporary condition which they can adapt to. In the long run, without access to land they slowly drown and the lack of brackish water complicates their molting, negatively affects their immune system and ultimately severely shortens their lifespan.

Red claw crabs are semi-aggressive even to their own kind, therefore it is recommended that each crab be provided with plenty of room and hiding places in order to be able to hold territories. If they are not kept in a species only tank there is usually a risk that they will catch and kill smaller fish that venture near them. A minimum of a 10 gallon tank is recommended for each individual, as nocturnal species they come out at night and explore their surroundings, thus the need for space. When it comes to foliage in the tank they can be very destructive, causing extensive damage to the stems on most live plants. They also like to eat bogwood or driftwood if it is present in the aquarium.